Thermoset polymers made from acid cured pre-polymer resins including phenol-formaldehyde resoles (PF), furane or furfuryl alcohol resins (FA), melamine-formaldehyde resins (MF), urea-formaldehyde resins (UF), and PF/FA, PF/UF, PF/MF, PF/UF/MF blends of such pre-polymer resins are used in the production of bulk moulding compounds, sheet moulding compounds, abrasives, grinding wheels, disks, friction materials, foam insulation, mineral insulation and glass fibre insulation, adhesives, inks, coatings, pre-pregs, electronics, laminates, filament winding, pultrusion, glass fibre composites, resin transfer moulding, vacuum bagging, carbon composites, bipolar plates, carbon electrodes, conductive composite electrodes, polymer electrolytes and membranes.
The ability to control the reactivity of a pre-polymer-catalyst system is important in terms of safety and processing economics. Thermosetting resins can be highly reactive when mixed with strong acids and dangerous exothermic reactions can result. The reactivity of a catalysed resin can be so rapid that the processing becomes impossible or very expensive. An example is where fabric is impregnated by soaking in a tank of resin and catalyst mixture before being further processed to form a composite sheet, wound pipe or extruded part. The resin and catalyst mixture should be a stable liquid long enough for the fabric to pass through the impregnation tank and then be reactive when heated to an elevated temperature without excessive reaction times.
In WO 2008/001089, a novel acid-cured conductive polymer is described. The acidic phenolic resin compositions disclosed in this document have been found to be highly reactive. In order to be able to have more control over the properties of mouldings formed from such compositions, a way to control the reactivity of the mix formulations has been sought.
U.S. Pat. No. 5,344,909 describes a latent catalysed phenolic resin composition containing a thermosetting phenolic resole resin and a latent catalyst consisting essentially of a primary or secondary amine salt of a strong acid for use in filament winding applications. Amines for preparing the latent catalyst are described as having a formula R—NH2 or R—NH—R. Normally, the R substituent will be selected from hydrocarbon moieties such as alkyl groups, generally a lower alkyl of 1 to 8 carbon atoms. However, alternative latent catalysts or retarders are needed.
For most applications where pre-mix production is not close to the moulding operation, it is desirable to have greater control over the reaction rate to enable large scale production, shipping, storage and reproducible moulding. Latent catalysts or retarders which can enable this are sought.
A way of ameliorating these problems has been sought.